1. Field of the Invention
The present invention relates to a ranging sensor system for a vehicle for calculating physical data between a subject vehicle and an object on the basis of a time between the transmission of a signal toward the obstacle and the reception of a signal reflected from the object.
2. Description of the Related Art
There are conventionally known ranging sensor systems using radar for measuring a distance between a subject vehicle and an object, for example, from Japanese Patent Publication No. 4700/86.
In calculating a physical data, e.g., the distance between the subject vehicle and the object, on the basis of the time between the transmission of the signal toward the obstacle and the reception of the signal reflected from the object, an error is included as a "vibration" in the obtained distance data. Moreover, the distance data to the object is obtained for the first time when the object is located in a range of a measurable distance and a measurable angle. No data is obtained, however, when the object is located in a range of a non-measurable distance or a non-measurable angle. Therefore, the data appears and disappears in a stepped manner, as shown by a solid line in FIG. 4.
Thereupon, if filtering is carried out to eliminate the vibration component of the error, detection data, when obtained for the first time, appears in a stepped manner as described above and hence, the data obtained after filtering of the detection data is varied, and a relatively long time is taken until the data obtained after the filtering converges.